The present invention relates to a new and improved apparatus and method for producing plastic foils or films or the like.
Generally speaking, the apparatus or installation of the present development for the production of plastic foils or films is of the type comprising a roller or roller member provided with a non-rotatable support or carrier member and a roller shell or jacket rotatable about the non-rotatable support or carrier member. This roller shell or jacket is supported at the non-rotatable support or carrier member by means of at least one support or pressure element--also known as a pressure-exerting or pressing element--exerting a support force in a pressing plane. Moreover, the roller shell or jacket cooperates with a counter roller or roll in such a manner that a fluent or flowable plastic material introduced into the nip or gap between the roller shell and the counter roller is cooled to a predetermined or desired solidification temperature.
2. Discussion of the Background and Material Information
Such apparatus for the production of plastic foils or films or plates are known to the art, for example, from the commonly assigned German Published Patent Application No. 3,300,251, published Aug. 4, 1983. The fluent or flowable plastic mass is conveyed between two rollers and, during solidification of the plastic mass, the one roller constructed as a controlled deflection roller is regulated so as to produce a predetermined thickness profile of the fabricated foil or plate or the like by means of the regulatable support force of the support elements This controlled deflection roller contains a single zone roll shell or jacket. However, such prior art foil or plate production apparatus is rather unsuitable for processing certain plastic materials which display a relatively sudden transition between their fluent and solid states throughout a relatively narrow temperature range. On the one hand, when processing such relatively rapidly solidifying plastics, for instance, polyethylene, the foil pressing and thickness regulation operation must take place at an exactly defined point in time at a relatively exact temperature. However, this is not required to that degree in the case of thermoplastic materials having a relatively large solidification range. On the other hand, rapidly solidifying plastics, during their solidification, tend to stick at the usually employed roller surfaces.